The production of standing waves in a flowing medium is known especially from the field of hydraulic engineering. Therefore, water is subsequently considered as a flowing medium.
Standing waves are often an unintended result of hydraulic-engineering plants or natural features or the result of intentional flow guidance in artificial constructions. Standing waves are much used by wave riders and canoeing sportsmen, among others.
One must differentiate between linear standing waves and breaking standing waves. Linear standing waves are characterized by a two-dimensional flow guidance and remain almost unchanged along an axis perpendicular to the direction of flow. Breaking standing waves can be produced only by a complex three-dimensional flow guidance.
The production of breaking standing waves is known from the German patent application DE 103 08 812 A1. The arrangement described there for producing standing waves in flowing water comprises a transverse structure arranged approximately perpendicular to the flow direction, a curved guide ramp that adjoins said structure upstream with contour lines that form an angle with the ramp, the acuteness of said angle increasing in the flow direction, and also a height-adjustable wave-generating body located downstream of the guide ramp, said wave-generating body being placed diagonally to an angle of attack relative to the flow direction. The arrangement is especially suitable for producing standing, especially breaking waves. The arrangement is incapable of producing linear standing waves due to the complex, three-dimensional flow guidance. The movable wave generating body is found directly below the standing waves in this arrangement. The arrangement of an unchanging wave-producing installation (wave generator) which is found directly below the standing waves is the objective of the German utility model application DE 200 19 358 U1 and also the German laid-open patent DE 101 02 805 A1. Arrangements that are similar in principle in laboratory systems or test channels are the objective of the international publications (“A stationary oblique breaking wave for laboratory testing of surfboards” by H. G. Hornung and P. Killen, Journal of Fluid Mechanics, 1976: “Hydrodynamics of Surfboards,” by Michael Paine, 1974. In the proprietary publications EP 0 547 117 B2 (DE 691 14 013 T3) and EP 0 629 139 B1 (DE 693 10 719 T2), devices for producing wave-like water surfaces of lower water depth and higher speed in artificial leisure devices are described. Here, a planar flow is produced that directly contacts a wave-shaped body. The installations that are conceptualized for flowing water according to the utility model DE 200 19 358 U1 and also the laid-open patent DE 101 02 805 A1 cannot produce waves for leisure activities with quality like that of devices with artificially produced flow.
It is known that inclined ramps with a height offset arranged downstream are suitable for producing linear standing waves, especially in the direction of flow (among others, e.g., from: “Production of waves and rollers for canoeing,” Report of the Institute for Waterways of the German Armed Forces University in Neubiberg on behalf of the Bayer Canoe Association, March 2004). Here, the wave formation in particular is induced by the abrupt delay of flow at the transition between the shooting flow movement on the ramp (Froude number >1) and a slower streaming flow movement downstream of the ramp (Froude number <1). Here, the water surface height beneath the device is of special importance for the formation of a standing wave.